This study has been done on the Yashirogo low moor area, which is located in the northeast of the Okitama plain in Yamagata prefecture. This area covers apporoximately 950 hectare, and the biggest depth of its peat deposits is apporoximately 9 meter. There is the apporoximately 5.3 hectare survival lake at the bottom of the deposits. This area has been mainly used as a paddy field, however, today there is a strong demand for a dry rice due to the rationalization of agriculture. Yet conservation of ill-drained paddy field and farm land consolidation often contradict each other.In order to explore a possible solution, this study will examine following six points ; 1) the actual condition of the land subsidence of the Yashirogo low moor area, 2) the influences of reuse of irrigation water upon the area, 3) the transition of the size of the survival lake, 4) the relationship between the road quality, 6) acid-proof properties of structures in the peat moor. The followings are the summary of
… More the results.1) Avarage 70 centimeter of foundation transition is acknowledged. The main reason of this transition is the desappearance of the surface portion. 2) Compared to the case of Hokkaido, the transition is remarkablly small. The reason is because this area is geographically closed and reuse of irrigation water is going on within it. This water management contributes to slowing down the deminishment of the area of the survival lake. 3) The road pressure consolidates the peat soil. The consequence shows that hydraulic conductivity is reduced to from one tenth to one fifteenth of the usual level. 4) The heavy metal related pollution of peat soil and water pollution which have been pointed out turn out to be nothing serious. The oxidization of structures in the area hardly matters, either.These results give a strong implication that conversation of ill-drained paddy field and development of surrounding areas can be achieved simultaneously.1)本地区は40年間で平均70cmの地盤の変動が確認された。この変動の主たる原因は表層の消失によるものであった。2)この変動は北海道の場合と比較するときわめて少ないものであた。その理由は、この地区は閉鎖系であり、末端部に水門を設け水位を常に一定に保ってるからである。さらに、灌漑期には水門を閉じ循環灌漑を行っているためである。このような水理と対応して白竜湖の面積の縮小速度も著しく遅くなってきた。3)道路荷重により泥炭は圧密れるが、泥炭の透水係数は水田の1/10〜1/15に低下することがわかった。4)かつて指された重金属汚染、水質については現在は問題はない。地区内構造物の酸化の問題も水質調査の果から問題はないことが明らかとなった。この結果は、湿原の保全と周辺地区の開発との両立に示唆を与えるものである。 Less